The present invention relates to a coal winning machine for use in mining operations.
More particularly, the invention relates to a coal winning machine having a cutting tool which may or may not be in form of a shearing drum. For convenience the invention will hereafter be described with reference to a machine of the type having such a shearing drum.
Coal winning machines with shearing drums are used rather widely in mining, particularly in underground mining of bituminous coal. The shearing drums rotate about an axis of rotation and are provided with cutting tools (so-called "picks") which are so mounted on the drum as to extend either radially or axially. Depending upon the particular radial or axial orientation the tools will contact the mine face (i.e. the coal and/or the rock matrix) with point contact or with line contact. These prior art arrangements suffer from the disadvantage that a very large number of cutting tools is required and that the wear of the tools is exceedingly high. In addition, and this is particularly true in the winning of bituminous coal, these arrangements produce an undesirably large amount of fines, i.e. small and smallest coal and rock particles and a concomitant evolution of dust. This is undesirable because of the danger of explosion and the health hazards which it represents (e.g. "miner's lung").
In an attempt to avoid these problems it has been proposed to provide a modified construction in which the helical flange surrounding the outer surface of the drum (and serving to guide separated pieces of coal and rock matrix away from the mine face so that they can drop upon a conveyor extending along the mine face) is provided with recesses into which mounting arrangements are welded wherein disk-shaped or plate-shaped cutting tools are turnably mounted. The mounting is such that these tools can turn about axes extending parallel to the axis of rotation of the drum, so that the tools can turn in the direction of drum advancement. With this proposal a considerably smaller number of cutting tools is required, in part because these plate-shaped tools have linear cutting edges. The wear on the cutting tools is reduced somewhat, and the down-time for repairs is decreased. Also, the undesired production of fines is substantially reduced.
Even this proposal, however, is far from satisfactory. The just-described modified equipment cannot readily be accommodated to different coal conditions (e.g. different seam thicknesses, different coal versus matrix conditions, and the like). Furthermore, the specific winning capacity of this equipment is relatively poor, primarily because none of the plate-shaped tools will cut for the subsequently following tool or tools sufficient free space, and finally the arrangement and construction of the tools themselves causes high friction in operation and thus results in wear which, although somewhat less than in the first-described types of equipment, is still far too high to be satisfactory.